The study found that people from Germany scored increasingly better on tests of brain processing speed done between 2006 and 2012. But, during the same time, the mental health and physical abilities of the study participants declined. All of the study volunteers were over 50 years old.

Decreases in mental and physical health were greatest in men aged 50 to 64 with low levels of education, the findings showed.

Improvements in brain processing speed may be due to higher levels of education and increased use of technology in daily life, the study suggested.

The study was published in the Aug. 31 online edition of the journal PLoS One. It was conducted by Nadia Steiber, a World Population Program researcher from the International Institute for Applied Systems Analysis (IIASA) in Austria.

In another study, IIASA investigators found that older people in England have also become smarter. Those findings were published in the September/October issue of the journal Intelligence.

"On average, test scores of people aged 50 and older today correspond to test scores from people four to eight years younger and tested six years earlier," Valeria Bordone, a researcher at IIASA, said in an institute news release.

Changing lifestyles may explain why older adults are getting smarter but losing ground in terms of mental health and physical fitness, according to Steiber, author of the first study.

"Life has become cognitively [mentally] more demanding, with increasing use of communication and information technology also by older people, and people working longer in intellectually demanding jobs. At the same time, we are seeing a decline in physical activity and rising levels of obesity," Steiber said in the news release.

More research is needed to see if these trends are happening in other countries, too, she added.